RF amplifiers are often implemented in various applications which require manipulation of an RF input power level to provide a desired RF output power level over a range of RF input power levels. Although termed “amplifiers,” such devices generally provide both RF input power attenuation as well as amplification, with the resulting proportionality between the input power and the output power referred to as the amplifier gain.
To achieve the desired gain, conventional RF variable gain amplifiers (VGA's) utilize operating point changing techniques and/or voltage variable attenuators (VVA's). To modify the operating point within the amplifier itself, the voltage and/or current applied to the transistors that are a part of the amplifier are varied. However, the RF amplifier linearity, noise, and impedance matching are also dependent upon the operating point of the transistors. Therefore, varying the gain of the RF amplifier through operating point changes can sacrifice non-gain performance of the RF amplifier over the RF amplifier gain range. As a result, the amplitude and frequency range in which RF amplifiers may adequately perform through operating point change implementations is limited. Similarly, VVA implementation results in degraded noise when used at the RF amplifier input, and degraded linearity when used at the RF amplifier output.
The disclosure will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.